1. Field of the Invention
The present invention relates generally to telephonic communications and more particularly to a cable-based telephony network providing a backup wireless communications path.
2. Background Information
FIG. 8 shows the basic architecture of a cable telephony network 10 providing cable-based telephone service.
The cable telephony network 10 typically includes one or more cable plants 18. Typically, each cable plant 18 comprises a broadband bi-directional, shared media, signal transmission system employing fiber optic trunks between a central signal distribution point known as a head-end or headend, and fiber nodes located in a neighborhood of customers of the cable network 10. Typically, coaxial cable is employed for distributing signals between the fiber nodes and equipment installed in the customer premises (generally referred to as customer premises equipment (CPE)).
The customer premises equipment used with the cable telephony network 10 typically comprises a terminal unit 36 for providing access by a telephone (not shown) to the cable telephony network 10 by a telephone (not shown). Each terminal unit 36 generally includes a cable modem (not shown), which electrically interfaces the terminal unit 36 to the cable plant 18. Each terminal unit 36 also typically includes a multimedia terminal adapter (not shown) which electrically interfaces the terminal unit 36 to the telephone or to a telephone like device.
The cable telephony network 10 also includes one or more cable modem termination systems 20 located at the head-end of each cable plant 18. The cable modem termination system 20 ensures that all terminal units 36 connected to the cable plant 18 are synchronized and have fair access to the cable telephony network 10. The signal modulation and the communication protocols used by cable modem termination system 20 and the terminal units 36 for communicating via the cable plant 18 typically conform to the standard Data-Over-Cable Service Interface Specification (DOCSIS) Radio Frequency Interface Specification, and utilize the standard Media Access Control (MAC) protocols. The combination of the cable plant 18 and the cable modem termination system 20 is typically referred to as a broadband cable system 50.
The cable telephony network 10 also typically includes an Internet Protocol (IP) network 22 and a PSTN gateway 30. Typically, the IP protocol network 22 is a private computer network using the known Internet Protocol. Telephone traffic between the customers of the cable telephony network 10 and customers of a public switched telephone network 30 typically flows via the cable modem termination system 20, the IP network 22 and the PSTN gateway 30. The cable modem termination system 20 and the PSTN gateway 28 perform the conversions of signaling and bearer traffic (call contents) for interfacing the IP network 22 to the cable plant 18 and to the public switched telephone network 30.
Typically, cable-based telephone service is supported by one or more computer based systems attached to the IP network 22. Such supporting computer systems typically include one or more call manager host computers 26 (i.e., call managers). Typically, each call manager 26 is associated with an assigned telephone office and provides for initiating, processing and forwarding call signaling information for telephone calls originating in that office. The cable-based telephone service is also typically supported by backend server host computers 24 which perform administrative tasks such as customer billing, and fault management host computers 34 which provide for control and management of various components (e.g., cable plant 18, cable modem termination system 20, etc.) of the cable telephony network 10.
To be competitive with telephony service offered by the public switched telephone network 30, the quality of a cable-based telephony service must be equivalent to that offered by the public switched telephone network 30. To that end, present day cable-based telephony networks 10 utilize redundant components in both the cable plant 18 and in the aforementioned support systems attached to the IP network 22, to provide high availability cable-based telephone service to the customers of the cable telephony network 10. In particular, the cable modem termination system 20, the back end server host computers 24, the fault management host computers 34, the call manager host computers 26, and the PSTN gateway host computers 28 are typically made redundant so that a failure of a single computer in one of the aforementioned systems does not render the cable-based telephony service to be degraded. The redundant components add extra cost and complexity to the cable telephony network 10. Many of the redundant components operate in a standby or passive mode until a failure occurs and consequently provide no benefit to a broadband cable customer of the cable telephony network 10 until the failure occurs.
In addition to providing redundant computer systems, each cable plant 18 typically includes a plurality of cable monitoring devices (not shown), generally known as a broadband test points, at selected points in the cable plant 18, to enhance the availability of the cable-based telephone service. The broadband test points measure selected characteristics of the signals being distributed in the transmission media of the cable plant 18 in order to provide means for detecting faults in the cable plant 18 and for isolating the faults to various segments of the cable plant 18. Typically, the signal characteristics measured by the broadband test points are reported to the fault management host computers 34 via the transmission media of the cable plant 18. Consequently, a catastrophic failure within the cable plant 18 can prevent receipt by the fault management host computers 34 of the values of the signal characteristics which are required to diagnose and repair the fault in the cable plant 18, thus negatively impacting the speed in which the full performance of the cable telephony network 10 can be restored from the fault condition.
It would be desirable to provide high availability cable-based telephone service for customers of the cable telephony network without requiring an excessive number of redundant components in the cable telephony network 10. Further, it would be desirable to provide the high availability telephone service using existing communication capabilities. Also, it would be desirable to provide an alternate means of communications between the cable monitoring devices and the fault management host computers 34.